The invention resides in an apparatus for the height-adjustable support of a wheel or an axle spring suspension on a vehicle body wherein a body-mounted spring support structure includes a cylinder piston unit by which a spring seat is slidably supported so that it can be extended under the control of a control member to which control fluid is supplied by a fluid supply pump.
EP 0 281 173 B1 discloses such a vehicle suspension with height adjustment capabilities. The arrangement disclosed therein is utilized in connection with a suspension system which includes two parallel spring elements. The spring elements are two coil springs arranged concentrically within one another. The cylinder-piston unit supports, by way of the hydraulically extendable spring support, only the inner coil spring. By the tensioning of this coil spring however, the characteristic spring curve of the suspension is changed among other characteristics.
The cylinder of the cylinder-piston-unit is mounted on the vehicle body. The spring is engaged by a piston-operated spring carrier cup. The spring carrier includes a sleeve which is disposed around, and sliding along, the cylinder. As a result, several seal and guide structures need to be arranged between the piston and cylinder as well as between the cylinder and the sleeve of which however only one is exposed to the pressurized fluid and is lubricated thereby.
It is an object of the present invention to provide an apparatus which actively prevents excessive spring strokes of particular wheels or axle portions in a simple manner. The apparatus must require only little space and few building components which are subjected to only little wear. Further, the apparatus is to be easily installed in motor vehicles and it should be possible to install it as after-market device without a need for changing the standard vehicles suspension and/or shock absorber system.